This invention relates to equipment for monitoring railway tracks, in particular for determining the rail profile.
Track recording vehicles are known, which include instruments for measuring many different attributes of a railway track. Such vehicles are expensive both to purchase and to operate, and consequently railway maintenance staff can inspect their lines only at infrequent intervalsxe2x80x94typically once a month on the busiest lines, and less frequently on other lines. Hand operated surveying trolleys are also known which are used to measure track parameters, but these are suitable only for short lengths of track, for example in sidings. Equipment to enable frequent and regular monitoring of track condition on substantially the entire railway network would be beneficial, particularly in providing information about the effect of railway traffic on track condition, and in quantifying the effect of maintenance. Such frequent monitoring will also enable railway staff to decide when to remove speed restrictions which may be imposed after track maintenance (such as design overlift); and indeed when to impose speed restrictions if track quality decreases. If track quality can be measured on a daily basis, this would also improve railway safety, and decrease the risk of derailment.
According to the present invention there is provided equipment for monitoring railway tracks, the equipment comprising a base station, at least one instrumentation package installed in a service vehicle, and automatic means for transferring data from the or each instrumentation package to the base station remotely and at intervals, the instrumentation package comprising sensors including at least one accelerometer mounted on the service vehicle, at least one position locating instrument arranged to provide positional information, and a computer arranged to receive data from the sensors and to process and store the data, characterised in that at least one accelerometer is mounted on a bogie of the service vehicle, and that the computer is arranged to process data from this accelerometer to determine linear displacements.
The instrumentation package is sufficiently small that it can be installed on a service vehicle, for example a passenger coach, without causing inconvenience to passengers or staff. Its operations are totally automatic, so no staff are required to monitor it. Consequently the equipment enables the track along which that service vehicle travels to be monitored on every journey, so the track may be monitored several times a day. Because it is installed in a service vehicle, no additional vehicle operating costs are incurred in performing the track monitoring.
The position locating instrument might use GPS. More precise information on position may be obtained using differential GPS, or by detecting the location of objects at known positions along or adjacent to the track such as points or crossings, APC (automatic power control) magnets, or AWS (automatic warning system) magnets. Dead reckoning methods may also be used, including inertial guidance systems, and measuring distance from known positions.
The sensors of the instrumentation package preferably comprise vertical accelerometers mounted on the bogie, one on each side of the bogie, above a wheelset, and also displacement transducers, one on each side of the bogie, arranged to monitor the distance between the wheelset and the bogie. Signals from these sensors enable the undulations of the top of each rail, i.e. the profile of the upper surface of the rail along its length, to be detected and measured. The computer may also receive data from other sensors, in particular a signal indicating the speed of the vehicle; such a signal is typically generated by the wheel slide protection system of the vehicle, or it may be generated by a speed sensor forming part of the instrumentation package. Sensors may also be provided to monitor the lateral position of the rails, and vehicle ride quality.